U.S. patent number 4,471,372 [Application Number 06/265,860] was granted by the patent office on 1984-09-11 for fet controlled triac.
This patent grant is currently assigned to Siemens Aktiengesellschaft. Invention is credited to Jen/o/ Tihanyi.
United States Patent |
4,471,372 |
Tihanyi |
September 11, 1984 |
FET Controlled Triac
Abstract
Bidirectional thyristor or Triac, including a semiconductor
body, first and second antiparallel-connected thyristor sections
integrated in the semiconductor body, each of the thyristor
sections having an anode side, a cathode side, an emitter zone on
the cathode side, a base zone on the cathode side, an emitter zone
on the anode side having a given conductivity type, and a base zone
on the anode side, a field-effect transistor being integrated into
the semiconductor body and having a control, a source, and a drain
terminal defining a load path, the source terminal being connected
to the emitter zone on the cathode side of the first thyristor
section and the drain terminal being connected to the base zone on
the anode side forming a connection through the load path of the
field-effect transistor, an auxiliary zone having the given
conductivity type of the emitter zone on the anode side of the
second thyristor section, the auxiliary zone being disposed between
the emitter zone on the cathode side of the first thyristor section
and the emitter zone on the anode side of the second thyristor
section, and a contact disposed on the auxiliary zone for
connection to a control current source.
Inventors: |
Tihanyi; Jen/o/ (Munich,
DE) |
Assignee: |
Siemens Aktiengesellschaft
(Berlin and Munich, DE)
|
Family
ID: |
6103208 |
Appl.
No.: |
06/265,860 |
Filed: |
May 21, 1981 |
Foreign Application Priority Data
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|
|
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May 23, 1980 [DE] |
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3019883 |
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Current U.S.
Class: |
257/125; 257/122;
257/126; 257/157; 257/E27.026; 257/E29.215; 327/455; 327/566 |
Current CPC
Class: |
H01L
29/747 (20130101); H01L 27/0688 (20130101) |
Current International
Class: |
H01L
29/66 (20060101); H01L 27/06 (20060101); H01L
29/747 (20060101); H01L 029/747 (); H01L 029/78 ();
H01L 027/02 (); H03K 017/60 () |
Field of
Search: |
;357/38,86,39,51,43,23R,23C,23VD ;307/252T,252B,311,305 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
H Eng., "The Field Effect Controlled Switch", Jul. 1970,
Microelectronics, vol. 3, #7, pp. 36-38..
|
Primary Examiner: James; Andrew J.
Assistant Examiner: LaMont; John
Attorney, Agent or Firm: Lerner; Herbert L. Greenberg;
Laurence A.
Claims
There is claimed:
1. Bidirectional thyristor or triac, comprising a semiconductor
body, first and second antiparallel-connected thyristor sections
integrated in said semiconductor body, each of said thyristor
sections having an anode side, a cathode side, a first emitter zone
on the cathode side, a first base zone on the cathode side, a
second emitter zone on the anode side having a given conductivity
type, and a second base zone of weak opposite conductivity type, a
first field-effect transistor being integrated into said
semiconductor body and having a control terminal, a control zone, a
source zone, a source terminal, a drain zone and drain terminal
defining a load path between the source terminal and the drain
terminal, the load path of said first field-effect transistor being
connected between said first emitter zone on the cathode side and
said second base zone in the anode side of said first thyristor
section, the source terminal being connected to said first emitter
zone on the cathode side of said first thyristor section, and
auxiliary zone having said given conductivity type of said emitter
zone on the anode side of said second thyristor section, said
auxiliary zone being disposed between said first emitter zone on
the cathode side of said first thyristor section and said second
emitter zone on the anode side of said second thyristor section,
and a contact disposed on said auxiliary zone for connection to a
control current source for controlling said second thyristor
section, said second base zone adjoining said first base zone and
said second emitter zone of said first thyristor section and said
first base zone and said second emitter zone of said second
thyristor section, and a resistor connected between said auxiliary
zone and said control terminal of said first field-effect
transistor.
2. Bidirectional thyristor or triac, comprising a semiconductor
body, first and second antiparallel-connected thyristor sections
integrated in said semiconductor body, each of said thyristor
sections having an anode side, a cathode side a first emitter zone
on the cathode side, a first base zone on the cathode side, a
second emitter zone on the anode side having a given conductivity
type, and a second base zone on the anode side of weak opposite
conductivity type, a first field-effect transistor being integrated
into said semiconductor body and having a control terminal, a
control zone, a source zone, a source terminal, a drain zone and a
drain terminal defining a load path between the source terminal and
the drain terminal, the load path of said field-effect transistor
being connected between said first emitter zone on the cathode side
and said second base zone on the anode side of said first thyristor
section, the source terminal being connected to said first emitter
zone on the cathode side of said first thyristor section, an
auxiliary zone having said given conductivity type of said emitter
zone on the anode side of said second thyristor section, said
auxiliary zone being disposed between said first emitter zone on
the cathode side of said first thyristor section and said second
emitter zone on the anode side of said second thyristor section,
and a contact disposed on said auxiliary zone for connection to a
control current source for controlling said second thyristor
section, said second base zone adjoining said first base zone, and
said second emitter zone of said first thyristor section and said
first base zone and said second emitter zone of said second
thyristor section, and a second field-effect transistor integrated
in said semiconductor body and having a control terminal connected
to the control terminal of said first field-effect transistor, a
source terminal and a drain terminal defining a load path, said
auxiliary zone contact being connected to an auxiliary voltage
through said load path of said second field-effect transistor.
Description
The invention relates to a bidirectional thyristor (Triac) with two
antiparallel-connected transistor sections which are integrated in
a semiconductor body and each have an emitter zone on the cathode
side, a base zone on the cathode side, an emitter zone on the anode
side and a base zone on the anode side.
Such a bidirectional thyristor, which will be called "Triac"
hereinbelow for simplicity, is described for instance in U.S. Pat.
No. 3,350,611. It substantially includes two antiparallel-connected
thyristor sections which are integrated in a single semiconductor,
the outer zones of which are each connected to each other through
an electrode. The Triac is switched-on by feeding a control current
to the base zone on the cathode side of one thyristor section.
Depending on the size of the Triac, this control current must be in
the order of magnitude of between 15 and 50 mA for reliable and
fast firing. It is not possible to drive the Triac directly by a
micro-computer of an LSI circuit, since these furnish in general
only output currents in the order of 1 mA.
It is accordingly an object of the invention to provide a
bidirectional thyristor or Triac which overcomes the
hereinafore-mentioned disadvantages of heretofore-known devices of
this general type, and to do so in such a manner that it can be
driven with substantially lower drive power, and especially
directly by micro-computers or LSI circuits.
With the foregoing and other objects in view there is provided, in
accordance with the invention, a bidirectional thyristor or Triac,
comprising a semiconductor body, first and second
antiparallel-connected thyristor sections integrated in the
semiconductor body, each of the thyristor sections having an anode
side, a cathode side, an emitter zone on the cathode side, a base
zone on the cathode side, an emitter zone on the anode side having
a given conductivity type, and a base zone on the anode side, a
field-effect transistor being integrated into the semiconductor
body and having a control, a source, and a drain terminal defining
a load path, the source terminal being connected to or located at
the emitter zone on the cathode side of the first thyristor section
and the drain terminal being connected to the base zone on the
anode side forming a connection through the load path of the
field-effect transistor, an auxiliary zone having the given
conductivity type of the emitter zone on the anode side of the
second thyristor section, the auxiliary zone being disposed between
the emitter zone on the cathode side of the first thyristor section
and the emitter zone on the anode side of the second thyristor
section, and a contact disposed on the auxiliary zone for
connection to a control current source.
In accordance with another feature of the invention, there is
provided a substrate of a given first conductivity type having
sides; the emitter zones on the cathode side of the thyristor
sections and the source zone of the field-effect transistor (FET)
being formed by zones of the given first conductivity type; the
emitter zones on the anode side, the base zones on the cathode
side, the control zone of the field-effect transistor and the
auxiliary zone being formed by zones of a given second conductivity
type; the zones of the second conductivity type being embedded in
one side of the substrate of the first conductivity type, the zones
of the first conductivity type being embedded in the zones of the
second conductivity type, and the drain of the field-effect
transistor and the base zones on the anode side of the thyristor
sections being formed by the substrate.
In accordance with a further feature of the invention, the zones of
the first conductivity type are formed by ion implantation.
In accordance with an added feature of the invention, the zones of
the second conductivity type are formed by diffusion and have equal
thickness.
In accordance with an additional feature of the invention, the
control zone of the field-effect transistor (FET) is formed by ion
implantation and is part of the base zone on the cathode side of
the first thyristor section.
In accordance with again another feature of the invention, there is
provided a substrate, the base zone on the cathode side of each of
the thyristor sections and the emitter zone on the anode side of
the other of the thyristor sections together form one of two
regions embedded in the substrate, each of the regions including a
relatively narrow strip making each region contiguous.
In accordance with again a further feature of the invention, there
are provided contacts disposed on the emitter zones on the anode
side, the regions being disposed on opposite sides of the
substrate, and the emitter zone on the cathode side of each of the
thyristor sections being opposite the contact for the emitter zone
on the anode side of the other of the thyristor sections.
In accordance with again an added feature of the invention, the
auxiliary zone is disposed in a recess formed in one of the regions
being defined by the base zone on the cathode side of the first
thyristor section, one of the strips, and the emitter zone on the
anode side of the second thyristor section.
In accordance with yet another feature of the invention, there is
provided a resistor connected between the auxiliary zone contact
and the control terminal or electrode of the field-effect
transistor (FET).
In accordance with a concomitant feature of the invention, there is
provided another field-effect transistor being integrated in the
semiconductor body and having a control terminal or electrode
connected to the control terminal or electrode of the
first-mentioned field-effect transistor, a source terminal, and a
drain terminal defining a load path, the auxiliary zone contact
being connected to an auxiliary voltage through the load path of
the other field-effect transistor.
Other features which are considered as characteristic for the
invention are set forth in the appended claims.
Although the invention is illustrated and described herein as
embodied in a bidirectional thyristor, it is nevertheless not
intended to be limited to the details shown, since various
modifications and structural changes may be made therein without
departing from the spirit of the invention and within the scope and
range of equivalents of the claims.
The construction and method of operation of the invention, however,
together with additional objects and advantages thereof will be
best understood from the following description of specific
embodiments when read in connection with the accompanying drawings,
in which:
FIGS. 1 and 2 are schematic and diagrammatic views of a first
embodiment example of the invention in two different operating
states;
FIG. 3 is a view similar to FIGS. 1 and 2 of a second embodiment
example of the invention;
FIG. 4 is a top plan view of a lateral Triac which makes use of the
principle according to FIGS. 1 and 2; and
FIGS. 5, 6 and 7 are cross-sectional views through the Triac
according to FIG. 4, taken along the lines V--V, VI--VI and
VII--VII, respectively, therein, in the direction of the
arrows.
Referring now to the figures of the drawing and first particularly
to FIG. 1 thereof, it is seen that a cross section through a
semiconductor body 1 of a Triac is shown diagrammatically therein.
The semiconductor body 1 contains two antiparallel-connected
thyristor sections integrated in the semiconductor body. The first
thyristor section of the left has a heavily n-doped emitter zone 2
on the cathode side, a base zone 3 on the cathode side, a base zone
4 on the anode side and an emitter zone 5 on the anode side. The
corresponding zones of the antiparallel-connected second thyristor
section on the right are 6, 7, 4 and 8, respectively. The emitter
zone 2 of the first thyristor section on the cathode side is
connected to the weakly n-doped base zone 4, which is common to the
two thyristor sections, by the load path of an FET 11. The term
"load path" is understood here to mean the path leading through the
source zone, control zone, and drain zone of the FET. The terminals
of the FET 11 are provided with reference characters S for the
source zone, D for the drain zone and G for the control or gate
terminal. An auxiliary zone 10 having the same conduction or
conductivity type as the zones 3, 8, 5 and 7 is connected between
the base zone 3 on the cathode side of the left-hand thyristor
section and the emitter zone 8 of the other thyristor section. In
the present case, this zone is heavily p-doped. Resistors 15 and 14
which serve in a known manner for improving the du/dt behavior are
connected between the zones 3 and 8, and 5 and 7, respectively. The
auxiliary zone 10 is electrically connected to the control terminal
G of the FET 11 through resistor 12.
With the polarity of the voltage +U.sub.A shown, a space charge
zone 13 which is shown as a shaded area, is built up in the zone 4.
With this polarity, the first thyristor section is biased in the
flipping direction and the pn-junction between zones 3 and 4 is cut
off. If a control signal +U.sub.G is applied to the control input
of the FET 11, the FET is switched into conduction and negative
charge carriers flow from the zone 2 through the load path of the
FET 11 into the zone 4. This causes emission of positive charge
carriers from zone 5, which move in the direction of the zone 3. At
the same time, zone 2 emits negative charge carriers which move
toward the pn-junction between zones 3 and 4. The pn-junction
between zones 3 and 4 is then biased in the flow direction and the
first thyristor section is fired.
With the polarity shown, the second (right-hand) thyristor section
is inoperative. The auxiliary zone 10 is likewise inoperative,
since the pn-junction between the zone 10 and the zone 4 is
blocked.
Since the FET 11 needs no current for switching-on except for a
capacitive current flowing between the control terminal G and the
source zone S, the Triac is switched on practically without
power.
If the polarity of the voltage (-U.sub.A) is reversed, somewhat
different conditions apply. These are shown in FIG. 2. It is
evident that the second thyristor section will now be biased in the
flipping direction, i.e. the pn-junction between the zones 7 and 4
will be blocked. If a positive signal is applied to the control
input of the FET 11, the FET is switched into conduction. The
signal potential "0" is therefore applied to the zone 4 in the
space charge-free part. At the same time, a small control current
flows into the auxiliary zone 10 through the resistor 12. The
auxiliary zone emits positive charge carriers into the zone 4,
since the pn-junction between zone 10 and zone 4 is now poled in
the forward direction. Therefore, among other things, the positive
charge carriers flow to the zone 7, which causes emission of
negative charge carriers from the zone 6. This in turn causes
emission of positive charge carriers from the emitter zone 8 on the
anode side of the right-hand thyristor section. The pn-junction
between the zones 7 and 4 is therefore biased in the flow direction
and the second thyristor section is fired.
In the switching state according to FIG. 2, the control voltage
source is loaded with a small current which is essentially
determined by the resistor 12. This current may be about 1 to 5 mA.
The load on the control voltage source, i.e. the microcomputer or
the LSI circuit, can be further reduced if the arrangement
according to FIGS. 1 and 2 is supplemented by an additional FET.
Such an arrangement is shown in FIG. 3. In the FIG. 3 embodiment
the auxiliary zone is connected to an auxiliary voltage source
-U.sub.H through a resistor 17 and the load path of a second FET
16, which can be integrated in the semiconductor body. The control
terminal of the FET 16 is electrically connected to the control
terminal of the FET 11. The small control current thus does not
come from the microcomputer in this embodiment but from a separate
current source which must be provided in any event as the power
supply of the microcomputer or the LSI circuit. The operation of
the arrangement according to FIG. 3 is analogous to that according
to FIGS. 1 and 2.
An operative lateral or planar embodiment of the Triac is shown in
FIGS. 4, 5, 6 and 7. The construction and operation will be
explained hereinbelow making reference to all of these figures.
The two thyristor sections and the FET are disposed on a substrate
20 which is weakly n-conducting. Two strongly p-conducting regions
21 and 22 are embedded in this substrate. The region 21 contains
the base zone 23 of the first thyristor section on the cathode side
and the emitter zone 32 on the anode side of the second thyristor
section. The above-mentioned zones 23 and 32 are connected to each
other by a narrow strip 39 which takes on the function of the
resistor 15 in FIG. 1. The region 21 has a cutout which is defined
by the zones 23 and 32 and by the strip 39. In this cutout there is
located the auxiliary zone 37 which corresponds to the auxiliary
zone 10 in FIG. 1. The zone 37 is provided with a contact 38, while
the zone 32 has a contact 33.
The region 22 includes the emitter zone 24 on the anode side of the
first thyristor section and the base zone 35 on the cathode side of
the second thyristor section. These zones are connected to each
other by a strip 40 which takes on the function of the shunt
resistor 14 in FIGS. 1 and 2. The zone 24 is provided with a
contact 31.
The zones 23, 24, 32, 35 and 37 and the strips 39, 40 are
advantageously made by the same diffusion step and therefore have
the same conduction or conductivity type and the same thickness. In
the embodiment example shown, these zones are heavily p-doped. A
zone 25 of the opposite conduction type is worked into the p-doped
zone 23. The zone 25 forms the emitter zone on the cathode side of
the first thyristor section. Similarly, a zone 36 of the opposite
conduction type, which forms the emitter zone on the cathode side
of the second thyristor section, is embedded in the zone 35. Zones
25 and 36 are advantageously prepared by ion implantation and have
the same thickness. They are provided with contacts 30 and 41,
respectively.
The control zone 26 of the FET is contiguous with the zone 23 of
the first thyristor section. The zone 26 has the same conduction
type but is made by ion implantation. The control zone 26 extends
at an angle to the surface of the substrate as seen in FIG. 5 which
can be achieved by a suitably formed mask. The control electrode 29
which is formed of polycrystalline silicon is used on the mask in
this embodiment. The flanks of the electrode 29 are bevelled, so
that an inclined arrangement of the control zone 26 in the
substrate 20 is obtained. The source zone is contiguous with the
emitter zone 25 on the cathode side of the first thyristor section
and is designated with reference character 19. The base zone on the
anode side of the thyristor sections and the drain zone of the FET
are formed by the substrate 20.
The contact 38 of the auxiliary zone 37 is connected through a
resistor 34 (corresponding to the resistor 12 in FIGS. 1 and 2) to
the control input of the FET, i.e. to the control electrodes 29.
The resistor 34 may be formed, for instance, of vapor-deposited
polycrystalline silicon.
The regions 21 and 22 are advantageously disposed opposite each
other in such a manner that the emitter zone on the cathode side of
the first thyristor section is opposite its emitter zone on the
anode side. The auxiliary zone 37 is advantageously opposite the
emitter zone 36 on the cathode side of the second thyristor
section, since these zones must interact electrically in the
operating condition shown in FIG. 2.
The operational sequence of the lateral Triac according to FIGS. 4
to 7 corresponds to the scheme explained in connection with FIGS. 1
and 2. The connections between the electrodes or contacts 31 and
41, and 30 and 33, respectively, are represented by discrete lines.
However, they are advantageously connected to each other by
vapor-deposited conductor runs, for instance, as is customary in
integrated circuits.
* * * * *